This invention relates to a device for checking that the bands joining filters to cigarettes have been sealed down, and more precisely to a device of a mechanical type which is able to detect faults in the sealing of the said bands and to subsequently reject the cigarettes found to be defective.
In accordance with the known practice, the fitting of the filters to the cigarettes is attended to by what are known as filter application machines, and this is done in the stages mentioned briefly below.
The cigarettes are placed two by two in axial alignment, and a filter cutting of a length double that for one single cigarette is interposed between them, along the same alignment and in contact with the extremities thereof. The ensemble constituted by the two cigarettes and the said cutting is joined by means of a band of paper material which is wound so as to cover the filter cutting and each of the said extremities over a distance of approximately 3 mm.
The terminal flaps of the said band, one of which previously gummed, are superposed one over the other.
A cutting device then divides each ensemble into two cigarettes complete with filter.
The said stages are concluded by devices which, rotating one of the cigarettes in each pair by 180.degree., create a succession of cigarettes aligned transversely with respect to their longitudinal axes.
During the said operation, however, cases are not infrequent of imperfect gumming or of either the mechanical stress of the cutting means or of the subsequent transfer means causing the terminal sealing flap on the joining band to open up and to protrude like a flag on the outside of the normal profile of the cigarette, as shown in FIG. 1.
It is obvious that this abnormal arrangement of the terminal flap of the band can cause various problems that are certainly not negligible during the subsequent operations of transferring and infeeding the cigarettes to the packeting machine.
In particular, cigarettes with the said fault that have not been immediately detected and eliminated, cause an interruption in the infeed flow inside the hopper in which the batches of cigarettes destined to be packeted are formed.
Not only does this act negatively on the production efficiency of the packeting machine but, for normal operating conditions to be resumed, it necessitates manual action being taken to remove the individual defective cigarettes from the said hopper.
The suitability can be seen from the foregoing of having a check on the condition of the band on each individual cigarette, and of this being carried out immediately the cigarettes exit from the filter application machine or wherever it is possible to effect the check on a succession of individual cigarettes.
Insofar as the Applicants herein are aware, devices are not known that have been expressly studied to trace and reject filter cigarettes having the described fault, that is to say, cigarettes in which a terminal flap on the band joining the cigarette to the filter, because of its being badly gummed, projects "flag" fashion on the outside of the normal profile of the cigarette, but only devices for checking the joining of the filter to the cigarette.
A first device with which to verify the mechanical strength of the said joint is described in British Pat. No. 1,086,935, and this envisages the provision of means for exerting axial stress on filter cigarettes whereby the filter tends to be separated from that part of the cigarette in which the tobacco is contained.
In one form of embodiment for the said device, the cigarettes are carried with a movement direction perpendicular to their axes, on a conveyor belt which supports them. The described check takes place in an area where a second belt is positioned overhead of the first conveyor belt, this being wound continuously around horizontal rollers, the said second belt extending parallel to the first belt at a distance away from this that is approximately a little less than the diameter of a cigarette.
At the side of the said conveyor belts there are two identical superposed belts that extend in a direction slightly horizontally oblique with respect to the direction in which the cigarettes move and between these the filters of the cigarettes being carried pass.
Thus the cigarettes move in a direction perpendicular to their axes, with the filters held firmly between the said latter pair of belts and the parts containing the tobacco gripped lightly between the first two belts. Because of the movement component of the pair of belts through which the filters pass being directed axially with respect to the cigarettes, axial stress is applied to these which tends to separate them from the filters, and which ought to do this when the jointing is poor.
Whilst, however, the said device may be efficient as regards the detection of cigarettes where the cigarette-filter joint is very obviously poor, it often fails to report the fault mentioned above where the terminal flap of the band joining the cigarette to the filter has been poorly gummed and protrudes in the form of a flag, for the detection of which the apparatus of the Applicants herein has been studied.
On cigarettes, in fact, where only a small flap on the jointing band has become unstuck, the tensile strength of the latter is often only very slightly different from that ascertained on normal cigarettes.
Furthermore, it should be noted that the device described subjects the cigarettes to undesirable stress which can cause them damage.
A second device, described in British Pat. No. 1,468,226, envisages the use of pneumatic means with which to trace openings in the rolling of the cigarettes.
With the said device, the cigarettes are carried in a movement direction perpendicular to their axes by slotted rotating cylinders onto which they are held by suitable suction means.
The check is effected by connecting at least one end of the cigarettes to a source of positive or negative air pressure, and by measuring the pressure of air applied. With cigarettes on which there are openings in the rolling or in the filter jointing area, leakages or infiltrations of air will occur, and the pressure values measured will thus vary with respect to those applicable to normal cigarettes.
The said device, which can also be used to trace cigarettes on which the filter jointing band has not been properly gummed, although it was not studied expressly for this particular purpose, presents difficulties, however, since it is considerably complex and necessitates the provision of devices with which to effect the check in the way outlined above. Then because of the said devices being positioned opposite one another, axially to the cigarettes, the slightest pressure applied to the ends of the latter can, especially at the high operating speeds of the fast moving check devices, cause wrinkles or folds in the cigarettes and thus consequential damage to them.